I don’t know about the West End, but over here, our Grantaires take their relationship with Gavroche very seriously. So here is a compilation of some Grantaire’s screaming in agony when Gavroche is killed :D

Joe Spieldenner, 4th National Tour (this is THE scream of agony. The official one)

John Rapson, Broadway (This was early in his run, where he actually said “OH GOD NO”. Very memorable.)